The following language tools of the COBOL2000 compiler are not supported when the program is run in the POSIX subsystem.
Dynamic subprogram call
Subprogram calls with the COBOL statement CALL identifier are illegal in POSIX and could abort the program run.
Program address identifier
Like “CALL identifier ...”, “ADDRESS OF PROGRAM identifier” requires dynamic loading at run time and is therefore not possible in POSIX.
ENTRY statement
The ENTRY statement is not allowed when the program is run under POSIX because it can only be used to define entry points to object modules, and under POSIX the compiler always generates link-and-load modules (LLMs).
Segmentation
As the compiler under POSIX always generates link-and-load modules (LLMs), COBOL program segmentation is not possible in POSIX.
File processing
Label handling when processing magnetic tapes is not possible in POSIX.
Checkpointing for restart of magnetic tapes is not possible in POSIX.
Shared updating of files is not possible in POSIX.
The usual LOCKING mechanism of UNIX is implemented in POSIX, so multiple instances of the same file could, for example, be opened concurrently for output.
The STANDARD-2 character set (International Reference Version of the ISO 7-Bit Code) specified in the ALPHABET clause is not supported in the CODE-SET clause. Any OPEN of this type will be currently rejected with FILE STATUS 30.
The messages COB9151 and COB9175 for errors on accessing POSIX files do not contain the DMS codes, but the corresponding SIS message numbers. This also applies to the “extended” file status returned to the COBOL object. Even the returned file status could deviate from the usually expected value (see section "I-O status").
READ PREVIOUS is not supported and is rejected with file status 96.
XML documents
The new language elements for reading XML documents need to be locaded dynamically at the program’s execution time and are therefore not possible in POSIX.